The Labour leader also said he was fighting a "battle of the bulge" to beat middle-age spread and described wife Justine Thornton as "the rock of my life".

In a highly personal interview with Now magazine the Labour leader was asked whether it was "weird" that he and Mr Balls had dated the same woman. He said: "We did both date her but there was a long time apart between me and Ed. Stephanie and I don't have any problems running into each other now."

Mr Miliband said he was a "late developer" when it came to romance.

"I was quite square and serious. Girls came a bit later - university and after", he said.

Asked if he had a fitness regime, the Labour leader acknowledged he had to be careful about what he ate and saw a personal trainer twice a week.

He said: "It's the battle of the bulge. It's so easy to be a man in your forties and to put on weight, it really is. I try to be careful with what I eat - I don't eat lots of desserts and bread with my meal. I see my personal trainer a couple of times a week - he gets me running. There are unflattering pictures to show for it."

The MP and Ms Thornton called each other "sweetie", Mr Miliband said, and added: "I really feel so lucky. She's so much the rock of my life. It sounds a bit corny. But I wouldn't be doing this job and I wouldn't be happy without her."

But Mr Miliband acknowledged she probably had a "long list" of things about him which annoyed her, including reading his BlackBerry at dinner time. He added: "I think it was Justine's idea to stop taking my phone on holiday. We have her phone and it means people are less likely to ring."

Your Comments

COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? customercare@belfasttelegraph.co.uk